1. Field of the Invention
The present invention relates to a cream base which can be used to manufacture stable cosmetics having high safety for skin and stable medicines such as skin external remedies and the like.
2. Description of the Prior Art
Usually, in the case that a cream base, i.e., emulsion is prepared, emulsification is carried out by using a surface active agent. However, the surface active agent has the problem of safety, and therefore much effort has been made to decrease the amount of the surface active agent as much as possible.
In order to meet this requirement, researches have been intensively conducted, but any emulsion which is excellent in safety and sensuosity has not been obtained so far.
Thus, as one measure for obtaining the satisfactory emulsion, the utilization of a colloidal hydrous silicate has been attempted so as to increase a yield point of an aqueous phase and to thereby stabilize the emulsion.
The colloidal hydrous silicate has a small particle diameter and can easily penetrate through fine spaces, and so the silicate can provide the emulsion with strong adsorbability and strong adhesion. A pH of a 2% aqueous silicate dispersion is in the range of 8 to 10.5, and an apparent specific gravity thereof is in the range of 0.7 to 1.0.
This kind of colloidal hydrous silicate has been used as a viscosity increasing agent or an auxiliary emulsifier, but in the case that the colloidal hydrous silicate obtained by a conventional technique is singly used, problems of sensuosity and safety are still present.
Japanese Patent Application Laid-open No. Hei3-83909 has suggested one solution. This is a cream base comprising a synthetic bentonite and silicon oil. In this cream base, the addition of the silicon oil permits decreasing the amount of the synthetic bentonite to thereby reduce creaky sense which the synthetic bentonite has, and the viscosity increasing function of the silicon oil and the fine particles of the synthetic bentonite function to maintain the stability of emulsification.
Furthermore, Japanese Patent Application Laid-open No. Hei3-221290 has suggested a cream base comprising a fatty acid dextrin and a colloidal hydrous silicate.
In this cream base, affinity for oily components can be enhanced by the fatty acid moiety, and affinity for aqueous components can be also enhanced by the dextrin moiety, whereby the stability of the emulsion can be heightened.
In an emulsification method of the cosmetic, a rotary homogenizer has often been heretofore used.
In recent years, a high-pressure type homogenizer has been developed, and as a result, emulsification power can be increased. Above all, a microfluidizer described in U.S. Pat. No. 4,533,254 is excellent. However, even if this kind of homogenizer is used, the conventional problems of separation and stability are still present.